1. Field of the Invention
The present invention relates to a universal joint construction and more specifically to a universal joint having two or more slotted members.
2. Related Art
Universal joints allow rotary motion to be transmitted from one shaft to another through an angle between the shafts. Such joints are used widely on propeller shafts and independently suspended driven wheels to accommodate suspension movement of the wheels. A well known universal is a Hooke's joint, which generally comprises a fork attached to each shaft with the tines of each fork extending toward the other shaft, with the forks arranged at right angles and interconnected by a cross piece to which they are pivotably attached. One characteristic of a Hooke's joint is that when the joint shafts are disposed at an angle other than 180.degree., the axial rotation of one shaft alternately leads ahead of and then lags behind the rotation of the other in the course of a single axial rotation. This lead-lag relationship is known in the prior art. See for example, Schwamb et al, Elements of Mechanism, sixth edition, revised by Doughtie, published by John Wiley and Sons, Inc., 1949, at pages 148-151, the disclosure of which is hereby incorporated herein by reference.
Some attempts have been made in the prior art to provide alternative mechanisms to a Hooke's-type joint and to produce a joint that has a more uniform relationship between the rotational speeds of the shafts. In a typical configuration of a joint of the prior art, one shaft has attached at the end a rigid tripod member which provides trunnions on which rotatable bearings or "rollers" are mounted, and the other shaft is equipped with a slotted member configured to receive the trunnions in the slots and to provide raceways against which the rollers bear. A typical arrangement is shown in U.S. Pat. No. 4,693,698 to Olson, II, dated Sept. 15, 1987 which shows a joint in which a tripod member 14 is fixedly mounted to shaft 12 to provide 3 equally spaced trunnions 21 that extend outwardly from the shaft. Each trunnion carries a roller bearing 25. The other shaft comprises a tulip member 13 having equally spaced petals or branches 15 separated by slots 16. Each slot is defined by a concave surface 17 on which roller bearings 25 bear. Related configurations are shown in U.S. Pat. No. 4,516,957; U.S. Pat. No. 4,175,407; U.S. Pat. No. 4,894,044 and U.S. Pat. No. 4,421,494.
U.S. Pat. No. 4,894,044 to Poulin et al dated Jan. 16, 1990 discloses a universal joint comprising a tripod 20 that is fixedly attached to shaft 22 at axial branches 30a, 30b and 30c (see e.g., column 3, line 54 through column 5, line 21). The branches, or trunnions, are equipped with rollers 36a, 36b, 36cthat bear against raceways in slots of a tulip element 42. The shafts are held together by disposing tripod 20 in a spherical intermediate element 44, and configuring the inner surfaces of the tulip element to slidably "grasp" the intermediate member.
In a common alternative arrangement, the tripod member is fixed to the shaft by securing the ends of the radial trunnions to a cylindrical fixture on the shaft so that the trunnions extend inward toward the longitudinal axis of the shaft. For example, U.S. Pat. No. 4,878,881 to Van Dest dated Nov. 7, 1989 discloses a universal joint in which a tripod member 3 having three arms with roller bearings 6 thereon (see FIG. 3) is welded to a bowl member 9 on shaft 11 at end portion 23 of each arm of the tripod. The mating shaft 2 is equipped with a tulip or petal portion 8 including raceways or roller tracks 7 to receive rollers 6. In addition, a spider element 24 is mounted in the petal portion 8 on shaft 2 to receive the central bowl portion of tripod 3. Tripod 3 is secured in spider 24 by means of a muzzle 32. Related configurations are shown in U.S. Pat. No. 3,990,267 and U.S. Pat. No. 3,818,721.
In all of the foregoing prior art joints, rotational motion is transferred from one shaft to the other by trunnions fixedly attached to one of the shafts.
U.S. Pat. No. 4,091,641 to Welschof, dated May 30, 1978, discloses a universal joint comprising an annular inner joint member 4 that is received within an annular cavity 2 between a cylindrical member 6 and an outer joint element 1. The cylindrical member and the outer joint element have axial slots to receive pins or "torque transmitting elements" 8, which pass through cylindrical openings (not slots) in the inner joint member 4 (see column 2, lines 14-16). The inner member has a variable axial relationship to the joint member, in other words, the intersection point of the respective axes of rotation moves when the inner member is withdrawn from the annular cavity, as indicated by a comparison of FIG. 1 and FIG. 3.